Using ruthenium catalysts to prepare cis-isomers of polycyclic aromatics



United States Patent 3,349,140 USING RUTHENIUM CATALYSTS T0 PREPARE CIS-ISOMERS 0F POLYCYCLIC AROMATICS Alfred W. Weitkamp, Lansing, Ill., assignor to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Filed Oct. 28, 1966, Ser. No. 590,215 9 Claims. (Cl. 260667) This is a continuation-in-part of copending application U.S. Serial No. 372,692, filed June 4, 1964 now abandoned.

This invention relates to the preparation of cis-isomers of hydrogenated aromatic hydrocarbons and more particularly to the preparation of increased amounts of saturated cis-isomers of bicyclic and tricyclic aromatic hydrocarbons. These cis-isomers are defined with respect to the common carbon atoms of the cyclic hydrocarbons and, in the case of the mono-methyl cis-isomers, include both the cis-syn and cis-anti isomers. The cis-isomers have the general characteristic of high heats of combustion and higher densities, and therefore are highly desirable as high-energy components of jet fuel.

Illustrative of the above-described properties of the cis-isomers, the cis-isomers of 2-methyldecalins have heats of combustion of about 1200 to about 3400 cal./ mole greater than the heats of combustion of the transisomers of Z-methyldecalins. In addition, the cis-syn-Z- methyldecalin has a density of 0.8812 gms./ ml. at 20 C. while trans-syn-2-rnethyldecalin has a density of 0.8568 gmsjml. at 20 C. Table I, shown below, indicates the relative properties of these and other various isomers of decalin, l-methyldecalin and Z-methyldecalin, as desirable products from the inventive process. In Table I, AH indicates the calculated differential in the heat of combustion for each isomer in a series, relative to the member in the series having the lowest heat of combustion.

Although the cis-isomers are preferred, they are thermodynamically less favored than the trans-isomers. It is therefore desirable to have a process in which the thermodynamics are avoided and increased amounts of the cis-isomers are produced.

It has been found unexpectedly that cis-isomers of hydrogenated polycyclic aromatic hydrocarbons having 2-3 fused cyclic units are produced in an amount which is substantially greater than the amount which is present at equilibrium when the bicyclic and tricyclic aromatic hydrocarbons are contacted with a catalyst comprising ruthenium in the presence of a hydrogen-affording gas under hydrogenation conditions. In this process, the amount of cis-isomers, which is much greater than the amount that would be present at equilibrium, is produced at a reasonable and practical reaction rate. As has been mentioned above, the cis-isomers are thermodynamically less favored than the trans-isomers. For example, at a temperature of 350 C., a mixture of cis-decalin and trans decalin will contain 86.8% trans-decalin and only 13.2% cis-decalin. At the same temperature, a mixture of 1- methyl trans-decalin and l-methyl cis-decalin will contain 86.2% l-methyl-trans-decalin and only 13.8% 1- methyl-cis-decalin. In the case of the 2-methyl-decalins at a similar temperature, the mixture will contain 87.6% 2-metihyl-trans-decalin and 12.4% Z-met-hyl-cis-decalin. An equilibrium mixture of the l-methyl-decalins at 25 C. will contain 98% l-methyl-trans-decalin and only 2% l-methyl-cis-decalin. Also, a mixture of the Z-methyl-decalins at 25 C. will contain 97.8% Z-methyl-trans-decalin and 2.2% 2-methyl-cis-decalin. These equilibrium values show that an equilibrium mixture of such polycyclic aromatic hydrocarbons is composed predominantly of the trans-isomers.

It has been found that through the use of the present invention, the product will be composed predominantly of the cis-isomers. It has been found that the increased amount of cis-isomers will be an amount which is greater than weight percent of the sum total of the cis-isomers and the trans-isomers.

It is further believed that the selectivity for producing the cis-oriented isomers is primarily dependent on a catalyst which comprises ruthenium. It is further believed that the mechanism involved in the present process includes the conversion of the fully unsaturated polycyclics having either the cis (as in naphthalene), cis-syn, or cisanti (as in methyl and dimethylnaphthalene) structures, and that at the higher temperatures the cis-oriented saturated polycyclics are converted to the thermodynamic favored trans-oriented isomers.

The process of this invention utilizes a feed containing substantial amounts of the polycyclic aromatic hydrocarbons; advantageously the polycyclics having 2-3 fused cyclic units including naphthalene, methylnaphthalene, dirnethylnaphthalene, and the like, and acenaphthalene and other tricyclic-fused aromatics, and preferably the fused bicyclic aromatic hydrocarbons. This feed may be obtained from the reformate product of various well-known catalytic hydroforming processes such as Ultraforming, Platforming, and the like which employ a platinum catalyst. For example, a reformer naphtha charge boiling in the range from C. to C. can be reformed over a platinum-on-a-lumina cat-alyst as described by Forrester, Conn, and Malloy in Petroleum Refinery, vol. 33, No. 4, p. 153 (1954) and in US. Patent No. 2,773,008. A fraction boiling in the range between C. and 240 C. is separated from the aromatics-rich portion of the resulting reformate and contains about 90 percent bicyclic aromatics. This fraction is well suited as a feed stock.

The process also has advantages when utilized with partially hydrogenated bicyclic aromatics such as the class identified at tetralins. When further hydrogenated by the'process of this invention, some of these tetralins yield even larger amounts of desired cis-isomers than are in the product of the hydrogenated bicyclic aromatics.

The catalyst employed in the present process is a catalyst comprising ruthenium. It can be used as a finely divided pure metal ruthenium powder. However, it can be supported on a nonhydrogenating carrier, such as charcoal or alumina in its various crystalline forms, with or without a solvent, such as acetic acid. It can be used also in its oxide form, but the metallic form is preferred. Advantageously, the ruthenium may be dispersed on a suitable support, the amount of. ruthenium varying from about 0.1 to about 6 weight percent, based on total weight. It is important that the support be a non-hydrogenating support so that hydrogenating components which do .not promote the formation of the cis-isomers will not be competing with the ruthenium and thus reduce the conversion to the. cis-isomers.

A typical method. of preparation of the catalyst is as follows: an alumina support may be impregnated with a solution of ruthenium chloride and the impregnated support may be calcined and steamed to convert the ruthenium to its oxide form.

A catalyst consisting of ruthenium on a carbon support The hydrogenation was carried out by charginga reactor withthe indicated feed and catalyst, after which the reactor was sealed and purged with hydrogen. The

contents of the reactor were then heated and stirred. The reactor temperature was thermostatically controlled. After purging with hydrogen, thepressure was increased to a maximum pressure in the order of 1000 p. s.i.g. while the reactor was being heated to the desired temperature. From 1 TABLE II Temp., Yield of cis- Run No. Feed Catalyst C.) Isomer, percent 1 Napht Ru/C 80 96.8 2 do 5% Ir/C 80 93. 7 3. ....(ln 5 (3/0 100 47.4 4 l-methyluaphthalene.-. 0 6% Bil/A1103- 200 98 5 do 0 6% PtlAhoan- 200 89 6. .....do 0 6% Rh/Al O; 100 85 7 0.6% Pd/Al 0 200 51 8 Z-methylnanh 0.6% RBI/A1203" 100 95.6 9. ----.rln 0.6% Rh/Al 0 100 83 10- do 0 200. 92 11 1,2-dimethylnaphthalene 150 90. 12. --.do 100 75. 13. .dn 7 200 31. 14 Acenaphthene; 200 95. 15. dn 200 36.

may be purchased from various commercial sources, for example, .Engelhard Industries.

A superatmospheric pressure, normally between about 300 and 3000 p.s.i.g. and preferably between about 500 and 2000 p.s.i.g., is employed in the hydrogenation zone. However, lower operating pressures tend to lower the hydrogenation reaction rate, although product composi-. tion is relatively unaffected.

The temperature employed for the more favorable yields of the cis-isomers is normally not more than about 300 C. and on thelow side is limited only by the reaction rate. Temperatures as low as C. are suitable although the reaction. rate is slow. Advantageously, the temperature is between about 100 and about 200 C.

Sufficient hydrogen is made available for saturating the polycyclic aromatic feed by maintaining an excess of hydrogen or other hydrogen-afiording gas in the reaction zone. The amount of such gas employed is not critical, although a sufiici'e'nt amount should be present to assure saturation of the feed. Typically about 1000 to 15,000 and preferably about 2000to 10,000 standardcubic feet of hydrogen-affording gas per barrel of feed is employed.

The following examples. are given in order to illustrate the beneficial effects of carrying out the present process to provide a product rich in the high density, high heat of combustion, cis-oriented isomers. It is to be understood that the following examples are given for illustrative purposes only and are not intended in any Way to limit the scope of the present invention.

Example 1 Naphthalene, l-methylnaphthalene, 2-methylnaphthalene, 1,2-dimethylnaphthalene, and acenaphthene were individually hydrogenated in the presence of the belowindicated hydrogenation catalyst and under various conditions of temperature as indicated in the following Table II. The amount of cis-isomer in each product was then determined.

hydrocarbon mixtures had compositions which were made.

up predominantly of cis-isomers when the hydrogenation component employed was ruthenium. In fact, in each case when ruthenium was used, the amount of cis-isomers obtained was greater than percent of the total amount of cis-isomers and trans-isomers.

Example 2 In this example, tetralin was hydrogenated in the presence of selected catalysts. The catalysts were used individually and each comprised the metal(s) as shown in Table III dispersed on a charcoal support. Each catalyst was made up of 5% metal and support. The hydrogenation members of each catalyst consisted of either individual hydrogenation metals or a mixture of hydrogenation metals. For each catalyst, a specified weight of hydrogenation metals was employed and the numbers represent milligrams. If the hydrogenation member were composed of one hydrogenation metal and mg. of that metal were employed, Table III would show the number 100 in front of the symbol for that metal. If the hydrogenation member were composed of more than one hydrogenation metal, the amount of each hydrogenation metal would appear before the symbol of that particular hydrogenationrnetal. For example, a catalyst which contained 50 mg. of ruthenium and 50 mg. of palladium dispersed on the charcoal support would be represented in,

Table III as 50 Ru, 50 Pd.

The reaction in each casewas carried out in a specially developed Micro-Magnedash reactor having a reactionchamber volume of about 5 ml. The hydrogenation wasv performed by charging the reactor with the specified catalyst and feed. The reactor was sealed and purged with hydrogen. The contents of the reactor were heated to the desired temperature and stirred. In each case, 0.5 ml. of tetralin was charged to the reactor. After the hydrogen purge, an initial hydrogen pressure of 1000 p.s.i.g. was created. The temperature employed and the time consumed for each reaction are presented in Table III, along with the conversion of the tetralin and the percent of cisand trans-isomers of the decalins formed.

support and under the specified temperatures presented in the following Table IV. Each catalyst was composed of 0.6 weight percent of the hydrogenation component on the gamma-alumina. The hydrogenation was performed as discussed in Example 2. Samples removed from the reactor were analyzed by gas chromatography. Please note that the term cis-isomers includes cis-syn and cisanti isomers and the term trans-isomers includes transsyn and trans-anti isomers.

TABLE III [Hydrogenation of Tetralin] Deealin, percent Run No. Catalyst Temp, Time, Conversion,

0. min. percent Cis- Trans- 100 3. 5 83. 6 93. 4 6. 6 100 163 51. 6 48. 5 51. 5 50 Ru, 50 P 100 4 82 83. 2 16. 8 10 R11, 90 Pd 100 8. 3 88. 6 79. 3 20. 7 5 Ru, 100 26 87 76.3 23. 7 100 R 80 4 75. 3 94. 7 5. 3 80 4.5 78 87.4 12.6 80 24 81.2 81. 19. 0 100 Pd 80 180 10 49. 6 50. 4 5 Ru, 95 P 80 32 76. 4 79. 4 20.6 100 Rh. 80 4 74 81.5 18. 5 Rh, 9 80 16 72 74.4 25. 6 00 80 5 79.4 92.0 8. 0 80 53 80. 3 81. 9 18. 1 50 Ir. 80 1. 6 12 91.8 8. 2 50 Ir. 80 4 27. 4 91. 8 8.2 50 11'. 80 7. 3 46. 8 91. 5 8. 5 50 Ir. 80 19 87. 7 93. 7 6. 3 01h... 25 1,200 92.5 7.5 20 Ir, 180 P 1,400 20. 3 80.9 19.1 100 Pt 25 480 2. 2 84. 0 l6. 0 20 Ft, 180 Pd 25 1, 400 4. 6 53. 9 46.1 0 Rh 25 7 78. 5 88.9 11.1 10 Rh, 90 19... 25 210 82.2 17.8 10 Ru, 90 Pd. 25 108 35. 5 83. 5 16. 5 25 6 79.8 94.5 5.5 25 1, 260 5. 6 46. 9 53. 1

As shown in the above table, the catalyst which pro- TABLE IV vided the greatest percentage of the cis-isomers at a reaction temperature of 100 C. was the catalyst which con- Temp" Trans sisted of 100 mg. of ruthenium d1spersed on the charcoal. Feed Catalyst 0. isomerst, isomerst, This catalyst was far superior to the catalyst which conparcel sisted of 100 mg. of palladium on charcoal. Although the catalysts WhlCh had ruthenium mixed W1th palladlum 1 methyltetmhn 88 3; 0 2% showed improved conversion of the tetralin and a higher 288 3.; 3.? concentration of the cis-isomer in the product than when 200 0 0 the hydrogenation component consisted solely of pa]- 5- h 1' 100 9 .5 ladrum, the resulting amount of the c1s-1somers did not met yltetram 100 5 2 equal the high percentage obtained with the catalyst con- 38g 3g- 31- g taining ruthenium as the sole hydrogenation component. 200 1 d ThlS phenomena was shown also by the data obtame zmethyltemfinzhu 100 94-8 5.2 from the runs which employed a reaction temperature of 100 5 2L 5 80 C. Likewise, when the reaction temperature was 25 38% $33 3% C., the greatest amount of cis-isomer was obtained with 200 1 the use of ruthemurn as the sole hydrogenation compo- 6 methy1tem1mm 100 94.7 5.3 nent. 500 3g. 2 13. 5

Individual methyltetralins were hydrogenated in the l presence of a catalyst which was composed of the below- [Plu 1 MeT impurity indicated hydrogenation component on a gamma-alumina 2 P1115 fi'MeT impmlty- It is clearlyshown that in each case when the methyltetralrin wa son q d w t th r hen u -melam ne catalyst, the resulting hydrocarbon minture contained an amount of the cis-ispmerS which was greater than 90% of the total amountof ci s-isomers and trans-isomers. h t In the aboveexampl'es, only one hydrogenation metal gave consistently mixtures which contained cis -isorners n an am nt eater than of he total m ts? cis-isomers and trans-isomers present. Thisihydrogenation metal was ruthenium.

What is claimed is:

1. A process for the preparation of an increased amount of cis-isomers of hydrogenated polycyclic aromatic hydrocarbons having 2-3 fused cyclic units whereinsaid increased amount is greater than 90% of the total amount of cis-isomers and trans-isomers which process comprises contacting polycyclic aromatic hydrocarbons with a catalyst consisting essentially of ruthenium on a non-hydrogenating support in the presence of a hydrogen-affording gas under hydrogenation conditions, including a temperature between about 25 C. and about 200 C. and a superatmospheric pressure which does not exceed 3000 p.s.i.g.

2. The process of claim 1 wherein said polycyclic aromatic hydrocarbons have 2 fused cyclic units.

3. The process of claim 1 wherein said polycyclic aromatic hydrocarbons include methylnaphthaletre- 4. The process of claim 1 wherein said polycyclic aromatic hydrocarbons include dimethylnaphthalene.

5. The process of claim 1 wherein said polycyclic aromatic hydrocarbons include acenaphthene.

6. The process of claim 1 wherein said catalyst consists of about 0.1 to about 6 Weight percent ruthenium on a non-hydrogenating support and wherein said temperature is between about C. and about 200 C. and said pressure is between about 500 p.s.i.g. and about 3000 p.s.i.g.

7. The process of claim 6 wherein a product rich in cis-isomers of the hydrogenated polycyclic aromatic hydrocarbons is recovered.

8. The process of claim 6 wherein said polycyclic aromatic hydrocarbons comprise tetralin.

9. The process of claim 6 wherein said polycyclic aromatic hydrocarbons comprise a mixture of methyltetralins.

References Cited UNITED STATES PATENTS 5/1965 Koch 260-667 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,349,140 October 24, 1967 Alfred W. Weitkamp It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, TABLE II, fourth column, line 4 thereof, for "200" read 100 column 5, TABLE III, second column, last line thereof, for "100 Pd" read 200 Pd column 6, TABLE IV, footnote 1 thereof, for "0.8" read 0.8% same table, footnote 2 thereof, for "2" read 2% Signed and sealed this 25th day of February 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A PROCESS FOR THE PREPARATION OF AN INCREASED AMOUNT OF CIS-ISOMERS OF HYDROGENATED POLYCYCLIC AROMATIC HYDROCARBONS HAVING 2-3 FUSED CYCLIC UNITS WHEREIN SAID INCREASED AMOUNT IS GREATER THAN 90% OF THE TOTAL AMOUNT OF CIS-ISOMERS AND TRANS-ISOMERS WHICH PROCESS COMRISES CONTACTING POLYCYCLIC AROMATIC HYDROCARBON WITH A CATALYST CONSISTING ESSENTIALLY OF RUTHENIUM ON A NON-HYDROGENATING SUPPORT IN THE PRESENCE OF A HYDROGEN-AFFORDING GAS UNDER HYDROGENATION CONDITIONS, INCLUDING A TEMPERATURE BETWEEN ABOUT 25*C. AND ABOUT 200*C. AND A SUPERATMOSPHERIC PRESSURE WHICH DOES NOT EXCEED 3000 P.S.I.G. 